This is very weird...

[Gambet]

Well, this has never happened to me. The only explanation i can give, is that you have "Hide npcs" enabled, so the only way you can see the npc's in the level is if you click "play", but in your case, you can see it which is very weird. Im not really sure what to tell you, im sure that the soccer ball didnt script itself.

[Xecutor]

It is weird.. I was working on the level one day and then I saved it and closed it.
The next day I opened the level and it was there...